know who it is. >> reporter: he was one of 2,000 men and women over the age of 70 who took part in the study. the mayo clinic found 19% of the men suffered from mild cognitive impairment compared to 14% of the women. mild cognitive impairment, or mci, is significant forgetfulness, but not severe enough to interfere with daily life. >> this was a surprising finding to us. >> reporter: what also makes these new findings so surprising is that women are more likely than men to get alzheimer's. fortunately, for leif, his wife's memory is still intact. >> i try to remember to ask him, daily, morning and evening, if he has taken his medication. >> reporter: doctors aren't sure why men are experiencing this memory loss more than women, but they're looking very closely at a possible clue. heart disease. >> when we look at the men who have mild cognitive impairment, they tend to have more of the vascular risk factors than women do, such as high blood pressure, diabetes, smoking history. >> reporter: the good news is, these are areas where doctors can intervene and potentially diminish the risk of developing significant memory loss. linsey davis, abc news, new york.